1. Field of the Invention
This invention relates to towers that house antennas for cellular, PCS, GPS or other wireless communications or signals. In particular, it relates to devices and methods for reinforcing towers that house such antennas.
2. Background
There are several types of tower structures (sometimes also called “poles”) that are used to hold land-based antennas for cellular/PCS communication. Where zoning requirements, restrictive covenants or other provisions or desires require aesthetically acceptable configurations, concealed (monopole) antenna towers are often used, These antennas are integrated within common pole-like objects such as, for example, flag poles, mono-palms and other type tree poles, street-lights, stop-lights and other utility poles (e.g., any type of monopole structure). The concealed antenna towers are configured so that the antennas are not externally visually apparent. The concealed antenna towers have a tubular structure with an internal, longitudinally-extending cavity that holds cables/transmission lines. The concealed antenna towers can hold one or several vertically stacked antenna canisters within a shroud or exterior that surrounds and encloses the antenna canisters, The concealed antenna towers are thus known as “poles” and “slick sticks.” See, e.g., U.S. Pat. Nos. 6,222,503 and 5,963,178, the contents of which are hereby incorporated by reference as if recited in full herein.
Other tower structures are used where there are no zoning requirements or less restrictive requirements therefore allowing taller structures not requiring concealed configurations and allowing for antennas to be visually seen and external to the pole structure.
Telecommunication structures in the United States are covered under TIA-222 Reference Standards (ANSI-approved standards) for minimum requirements for the design and analysis of towers and monopoles that support communication antennas and equipment. However, not all towers have the same design, capacity or structural reliability. Various shaft upgrades and reinforcing designs have been proposed for the towers so that the towers can add more antennas to existing monopoles to respond to the growing demand. Field bolted, rather than welded, designs have been developed in response to the risks posed by field welded systems, including flat plate systems, folded plate systems, and heavy channel systems. See, e.g., Brian Reese, Upgrade Monopole Steel Towers with Steel Channel, AGI, September 2009, pp. 37-43 (www.agl-mag.com). and U.S. Pat. No. 6,915,618 and US Patent Application Publication No. 2003/0010426, the contents of which are incorporated by reference as if recited in full herein.
Despite the number of reinforcement designs used, some reinforcement designs have resulted in tower failures such as fires and collapsed pipe or towers. See, e.g., David Hawkins, Discussion of Current Issues Related to Steel Telecommunications Monopole Structures, 2010 Structures Congress, pp. 2417-2438, ©2010 ASCE.
There remains a need for alternate, reliable tower reinforcement designs.